package task;

import java.util.Scanner;

public class Task5_3 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int n = input.nextInt();
        System.out.println(fib(n));
    }
    public  static int fib(int n){
        if(n == 1 || n == 2){
            return 1;
        }else{
            return fib(n - 1) + fib(n - 2);
        }
    }
}
